Self-washing insulators



Nov. 21, 1967 H. MEIER I 3,354,262

SELF-WASHING INSULA'IORS Filed May 15, 1967 United States Patent 4 Claims. ((31. 174-211 ABSTRACT OF THE DISCLOSURE The employment of one or more helical fins formed integrally with an insulator of the type consisting of a stem formed by a body of revolutions, said fins having at least three surfaces protuberances, the height of which decreases, in proportion, in a direction away from the stem of the insulator to improve its resistance to flashover voltage in a polluted atmosphere.

The present invention relates to improvements in insulator fins, notably in high voltage self-washing insulators, that is, insulators which clean themselves automatically due to the trickling of rain water, such as insulators consisting essentially of a solid or hollow stem or shank on which one or more helical fins are wound.

It is the object of the invention to provide improvements in insulators having fins, the profile of which comprises protuberances at the end and on the upper and lower face of the fin, so as to improve the properties of the insulators, notably their fiashover voltage in a polluted atmosphere.

The invention consists notably in the definition of certain dimensions or dimensional ratios relative to the fin in respect of which the applicant has ascertained that there is a substantial improvement in the properties of the insulators.

The insulator fin according to the invention is remarkable notably in that it comprises at least three protuberances, the dimensions of the fin being such that the ratio of the terminal thickness of the fin and of the fin pitch is lower than 0.5, the length of the fin is greater than 20 mm., the fin thickness ranges between 6 and 18 mm., and the pitch length of the fin ranges between and 50 mm.

According to a further feature of the invention, the ratio of the end thickness of the fin and comprises between 0.3 and 0.45, the length of the fin comprises between 25 and 5-0 mm., the thickness of the fin comprises between 8 and 12 mm., and the pitch length of the fin comprises between 18 and 35 mm.

According to yet a further feature, the fin comprises a profile having spaced teeth, the radius ofthe relief portions being less than the radius of the recessed portions.

According to yet a further feature of the invention, the fin comprises protuberances, the height of which decreases in proportion as the end of the fin is approached.

According to yet a further feature of the invention, if the apex of the two proturberances nearest the stem of the insulator is joined by one line and the depressions or recesses formed between the said protuberances are joined by a further line, the said lines constitute half-angle cones less than 12 in respect of the outer cone envelope and less than 7 in respect of the inner cone envelope, the end protuberances being contained within the outer cone envelope.

Further features of the invention will be disclosed in the following description which is given purely by way of nonlimitative example of forms of embodiment of insulator I ns according to the invention. It is to be made quite clear that the special features disclosed both in the text and in the drawings form a part of the invention.

In the drawings:

FIGURE 1 shows, diagrammatically, in section, a fin profile of known type.

FIGURE 2 shows, diagrammatically, in section, a fin profile according to the invention.

FIGURE 3 shows a further embodiment of the fin profile according to the invention.

The figures show a section through one turn of the helical fin having:

Pitch p Fin depth a Fin end thickness e FIGURE 1 shows a fin of known type comprising two protuberances of the same height, the half-view on the left shows a solid stem or shank, Whereas the right-hand half-view shows a hollow stem or shank.

In the form of embodiment according to the invention shown in FIGURE 2, the fin comprises three protuberances which are very considerably rounded and comprise an end protuberance 1 and two intermediate protuberances 2 and 3, the height of the protuberances decreasing in proportion as one moves away from the stem 4 of the insulator. The ratio e/p is selected to be lower than 0.5, and is preferably between 0.3 and 0.5, the length a is greater than 20' mm., preferably between 25 and 50 mm, the thickness e is between 6 and 18 mm., preferably between 8 and 12 mm., the pitch 1 varies from 15 to 50 mm., preferably from 18 to 35 mm., the radius r of the relief portions is approximately of the radius R of the central recessed portion. In the case of a fin having a depth of 40 mm., the radius of the relief portions will be approximately 3 mm., the radius of the recessed portions will be, proceeding from the stem towards the edge 543.5 mm. In the case of varying depth of the fin, these dimensions will be modified approximately in the same ratio as that of the measurement of the said depth. Since the height of the protuberances decreases in proportlon as one moves and the recesses 5, 6, 7 formed between the said protuberances are joined by a line, it will be found that these lines constitute half-angle cones b which are less than 12 in respect of the outer cone envelope 8 and c which are less than 7 in respect of the inner cone envelope 9. Furthermore, the end protuberance 1 is contained within the outer cone envelope 8, for example, b will be equal to 106, and c to 67.

In the form of embodiment illustrated in FIGURE 3, the fin comprises protuberances having spaced teeth leaving a considerable recess between them, the radius of the central relief portion and that of the relief portion adjacent the stern being approximately 4 of the radius of the central recessed portion, the end relief portion 1 having a radius double that of the further relief portions 2 and 3.

In the case of a fin having a depth of 32.5 mm., the radius of the central relief portion 2 and the relief portion adjacent the stem 3 will be approximately 1 mm. The radius of the end relief portion 1 will be approximately 2 mm. The radius of the recessed portions will be, proceeding from the stem towards the edge, 5.54.5 4.5 mm. With diflerent fin depths, these dimensions will be modified approximately in the same ratio as that of the measurement of the said depths.

The enveloping curves of the apex of the protuberances and of the fin recesses constitute half-angle cones b less than 12 in respect of the external cone envelope, and 0 less than 7 in respect of the inner cone envelope, for example, b will be equal to 7 and c to 45.

' The table shown hereinbelow gives, by way of example, some numerical values for certain dimensions in mm. and certain dimensional ratios relating to some embodiments of known fins and fins according to the invention. The fins 1 and 2 are of the type shown in FIGURE 1, the fins 3 have a profile corresponding to that of FIGURE 2, the

fins 4 and 5 a profile corresponding to that of FIGURE 3.

TABLE 1 Helix pitch, p 40 26 26 22 19.3 Fin depth, a 35 26. 5 38. 5 32. 5 28 End thickness of the fin 15 10 8 8 Trailing edge per fin, If. 122 82 114 90 81. 5 Ratio, a/p 0.875 1. 02 1. 48 1. 48 1. 45 Ratio, e/p 0.375 0.385 0.385 0. 364 0. 415 Ratio, I f /p 3.05 3. 4. 38 4.09 4. 22

Constantly applied voltage: 52 kv.

Pollution cycle: 3 h. deposit of dust at the rate 750 g. per hour, using a kaolin dust, followed by 3 h. of saline mist (solution of 31 g. of NaCl per litre of water), at the rate of 16 litres per hour.

It is found that, with a series of four tests, the insulator equipped with conventional fins according to type 1 held 2 2- 3- 2 cycles, whereas the insulator equipped with fins according to 4 held 3-344 cycles before flashover.

If insulators are manufactured of the type known under the name of Spirelec, this being a mark registered by the applicant, with a fin corresponding to the conventional profile type 2 and with a fin corresponding to the profile type 3 having spaced teeth in accordance with the invention, and if the insulators are comparatively subjected to dust-depositing cycles identical with those described hereinabove, it is found that the insulator of conventional type holds 3 cycles, whereas the insulator provided with fins according to the invention holds 4 cycles.

If, for these same insulators, the value of the leakage current is measured in pa. (measured under conventional rain-3 mm./minute, 10000 ohm cm.) for different voltages in kv., the results shown in Table 2 are obtained, and these show clearly the advantage achieved by designing the fin in accordance with the invention.

4. The dust-depositing cycle is 3 h. of kaolin by3h.salinernist, Each cycle being separated by washing for 5 minutes with rain of conventional intensity (3 mm./minute) and with a resistivity of 7000 ohm cm., it is found that the insulator having a conventional fin withstands 21 cycles before fiashover, the insulator having a fin according to the invention withstands 38 cycles, that is, an improvement of 81%.

dust, followed These examples show the advantages achieved in insulators by adopting a profile according to the invention as defined hereinabove with regard particularly to the resistance to disruption in a polluted atmosphere. It is known that it is at the present day held that these functioning conditions are among the most significant when appreciating the value in use of an insulator.

It will be clearly understood that the fin profile according to the invention may be applied equally well to an apparatus insulator and to a line insulator, to a support column or to an envelope, and equally well to a suspension insulator of'the type having a long stem for example, whatever the material used or the details in respect of design, manufacture and assembly of the insulating part.

Of course, the invention is in no way limited to the modes of embodiment described and illustrated, which have been given purely by way of example; in particular, it will be possible, without exceeding the scope of the invention, to modify certain arrangements and to replace certain means by equivalent means.

While the invention has been particularly shown and described with reference to preferred embodiments thereof, it will be understood by those skilled in the art that the foregoing and other changes in form and details may be made therein without departing from the spirit and scope of the invention.

What is claimed is:

1. In an insulator of the type comprising a stem which constitutes a body of revolution, the improvement comprising one or more helical fins integrally formed therewith having at least three surface protuberances, with the dimensions of each fin being such 'that; the ratio of end thickness of the fin to fin pitch is less than 0.5, the radial length of the fin is greater than 20 mm, the thickness of the fin is on the order of 6 to 18 mm., and the fin pitch is on the order of 15 to 50 mm.

2. The insulator as claimed in claim 1 wherein the ratio of end thickness of the fin to the pitch of the fin is between 0.3 and 0.45, the radial length of the fin is between 25 and 50 mm., the thickness of the fin is between 8 and 12 mm, and the pitch of the fin is between 18 and 35 mm.

3. The insulator as claimed in claim 1 wherein the fin includes an end protuberance and at least two inter- TABLE 2 Leakage Current Voltage applied l-;. i 20 40 Insulator havingaconventional fin, type 2. 780 1,680 3, 400 5,000 6,700 8,600 10,800 12,600 Insulator having afin according to the invention, type 5. 360 910 1,500 2,010 2, 700 3,700 4, 500 5,600

If, on the other hand, a comparison is effected bemediate protuberances, and wherein the radius of the tween two insulators of the Spirelec type of a model relief portions of the fin forming the protuberances is differing from a Of he Preceding insulators, one thereless than the radius of the recessed portions therebetween. being Provided W a fin C P known 4. The insulator as claimed in claim 3 wherein the P yp 1, Whereas tha 91116? 15 P Q a 70 radius of the relief portions of the fin is approximately .of the profile WP? acconlmg n? om If three fourths of the radius of the central recessed portion. they su i t 'te dlsmptlve voltage test under 5, The insulator as claimed in claim 3 wherein the Ponlmon: e radius of the relief portion of the fin is approximately The voltage applied is .6 3 kv fora chain of two insuone fourth of the radius of the central recessed portion.

1am, i w 1 75 Th? 1 51.11.310! as claimed in claim 3 wherein the radius of the relief portion forming the protuberance at the end of the fin is double that of the innermost relief portion.

7. The insulator as claimed in claim 1 wherein the surface protuberances of the fin comprise a profile having spaced teeth.

8. The insulator as claimed in claim 1 wherein the height of the protuberances decreases, in proportion, in the direction away from the stem of the insulator toward the fin end to form a cone outer envelope, the half angle at the apex of the cone outer envelope of the protuberances being less than 12.

9. The insulator as claimed in claim 8 wherein the recesses formed between the protuberance define an internal cone envelope, the half angle at the apex of which is less than 7".

10. The insulator as claimed in claim 8 wherein the fin end protuberance is contained within the outer cone envelope formed by the intermediate protuberances.

References Cited UNITED STATES PATENTS 3,003,022 10/1961 Meier 174-211 FOREIGN PATENTS 1,286,554 1/1962 France.

436,397 10/1935 Great Britain.

15 published Mar. 31, 1960, pp. 174-212.

LARAMIE E. ASKIN, Primary Examiner. 

1. IN AN INSULATOR OF THE TYPE COMPRISING A STEM WHICH CONSTITUTES A BODY OF REVOLUTION, THE IMPROVEMENT COMPRISING ONE OR MORE HELICAL FINS INTEGRALLY FORMED THEREWITH HAVING AT LEAST THREE SURFACES PROTUBERANCES, WITH THE DIMENSIONS OF EACH FIN BEING SUCH THAT; THE RATIO OF END THICKNESS OF THE FIN TO FIN PITCH IS LESS THAN 0.5, THE RADIAL LENGTH OF THE FIN IS GREATER THAN 20 MM., THE THICKNESS OF THE FIN IS ON THE ORDER OF 6 TO 18 MM., AND THE FIN PITCH IS ON THE ORDER OF 15 TO 50 MM. 